1. Field of the Invention
The present invention relates to an image forming apparatus capable of, in parallel with printing of a set of image data, image-processing of another set of image data in an image processing portion.
2. Description of the Related Art
As a copying machine or the like, which is a kind of image forming apparatus, there is a so-called multi-access type that is capable of simultaneously executing print recording of a set of image data and reading of another set of image data. As the multi-access type of copying machine, because of a strong desire for increase of a processing speed, there is the one equipped with two image processing portions that are processing circuits so as to be capable of executing image processing for print recording of a set of image data and image processing of another set of image data having been read in parallel.
However, an image processing portion that executes high-grade image processing is expensive and hence causes a rise in cost of the apparatus. Therefore, such an image forming apparatus is demanded that is equipped with only one image processing portion to keep the cost low and processes at a high speed.
As means for increasing a processing speed in the multi-access type of image forming apparatus, use of a recording sheet interval formed by recording sheets when a plurality of recording sheets are subjected to print recording, that is, an interval between execution of one print recording job and execution of a next print recording job can be considered. As a prior art focusing on the recording sheet interval, there is an image forming apparatus capable of executing a plurality of jobs by interrupt, and the image forming apparatus detects a recording sheet interval while one job is in progress and executes a job not executed at present as an interrupt job in a case where the job may be executed within the recording sheet interval (refer to Japanese Unexamined Patent Publication JP-A 2004-173291).
However, JP-A 2004-173291 discloses only increase of processing efficiency by executing an interrupt print job in a recording sheet interval during execution of an ordinary print job, and does not disclose at all a solution to limit the number of the image processing portions to one and to execute print recording of a set of image data and image processing of another set of image data in parallel in order to reduce the cost and increase processing efficiency, in the multi-access type of image forming apparatus as described before.